This invention relates to certain Trans cyclopentanyl purine analogs which are useful as immunosuppressants.
Immunity is concerned with the recognition and disposal of foreign antigenic material which is present in the body. Typically the antigens are in the form of particulate matter (i.e., cells, bacteria, etc.) or large protein or polysaccharide molecules which are recognized by the immune system as being xe2x80x9cnon-selfxe2x80x9d, i.e., detectably different or foreign from the animals own constituents. Potential antigens can be a variety of substances, often proteins, which are most frequently located on the outer surfaces of cells. For example, potential antigens can be found on pollen grains, tissue grafts, animal parasites, viruses, and bacteria. Once the antigenic material is recognized as xe2x80x9cnon-selfxe2x80x9d by the immune system, natural (non-specific) and/or adaptive immune responses can be initiated and maintained by the action of specific immune cells, antibodies and the complement system. Under certain conditions, including in certain disease states, an animal""s immune system will recognize its own constituents as xe2x80x9cnon-selfxe2x80x9d and initiate an immune response against xe2x80x9cselfxe2x80x9d material.
An immune response can be carried out by the immune system by means of natural or adaptive mechanisms, each of which are composed of both cell-mediated and humoral elements. Natural mechanisms for immune response refer to those mechanisms involved in essentially non-specific immune reactions which involve the complement system and myeloid cells alone, such as macrophages, mast cells and polymorphonuclear leukocytes (PMN), in reacting to certain bacteria, viruses, tissue damage and other antigens. These natural mechanisms provide what is referred to as natural immunity. Adaptive mechanisms for immune response refer to those mechanisms which are mediated by lymphocytes (T and B cells) and antibodies which can respond selectively to thousands of different materials recognized as xe2x80x9cnon-selfxe2x80x9d. These adaptive mechanisms provide what is referred to as adaptive immunity and lead to a specific memory and a permanently altered pattern of response in adaptation to the animal""s own environment. Adaptive immunity can be provided by the lymphocytes and antibodies alone or, more commonly, can be provided by the interaction of lymphocytes and antibodies with the complement system and myeloid cells of the natural mechanisms of immunity. The antibodies provide the humoral element of the adaptive immune response and the T-cells provide the cell-mediated element of the adaptive immune response.
Natural mechanisms of immune response involve phagocytosis by macrophages and PMN whereby foreign material or antigen is engulfed and disposed of by these cells. In addition, macrophages can kill some foreign cells through its cytotoxic effects. The complement system which is also involved in natural immunity is made up of various peptides and enzymes which can attach to foreign material or antigen and thereby promote phagocytosis by macrophages and PMN, or enable cell lysis or inflammatory effects to take place.
Adaptive mechanisms of immune response involve the actions against specific antigens of antibody secreted by B-lymphocytes (or B-cells) as well as the actions of various T-lymphocytes (or T-cells) on a specific antigen, on B-cells, on other T-cells and on macrophages.
Antibodies, which are responsible for the humoral aspect of adaptive immunity, are serum globulins secreted by B-cells with a wide range of specificity for different antigens. Antibodies are secreted in response to the recognition of specific antigens and provide a variety of protective responses. Antibodies can bind to and neutralize bacterial toxins and can bind to the surface of viruses, bacteria, or other cells recognized as xe2x80x9cnon-selfxe2x80x9d and thus promote phagocytosis by PMN and macrophages. In addition, antibodies can activate the complement system which further augments the immune response against the specific antigen.
Lymphocytes are small cells found in the blood which circulate from the blood, through the tissues, and back to the blood via the lymph system. There are two major subpopulations of lymphocytes called B-cells and T-cells. B-cells and T-cells are both derived from the same lymphoid stem cell with the B-cells differentiating in the bone marrow and the T-cells differentiating in the thymus. The lymphocytes possess certain restricted receptors which permit each cell to respond to a specific antigen. This provides the basis for the specificity of the adaptive immune response. In addition, lymphocytes have a relatively long lifespan and have the ability to proliferate clonally upon receiving the proper signal. This property provides the basis for the memory aspect of the adaptive immune response.
B-cells are the lymphocytes responsible for the humoral aspect of adaptive immunity. In response to recognition of a specific foreign antigen, a B-cell will secrete a specific antibody which binds to that specific antigen. The antibody neutralizes the antigen, in the case of toxins, or promotes phagocytosis, in the case of other antigens. Antibodies also are involved in the activation of the complement system which further escalates the immune response toward the invading antigen.
T-cells are the lymphocytes responsible for the cell-mediated aspect of adaptive immunity. There are three major types of T-cells, i.e., the Cytotoxic T-cells, Helper T-cells and the Suppressor T-cells. The Cytotoxic T-cells detects and destroys cells infected with a specific virus antigen. Helper T-cells have a variety of regulatory functions. Helper T-cells, upon identification of a specific antigen, can promote or enhance an antibody response to the antigen by the appropriate B-cell and it can promote or enhance phagocytosis of the antigen by macrophages. Suppressor T-cells have the effect of suppressing an immune response directed toward a particular antigen.
The cell-mediated immune response is controlled and monitored by the T-cells through a variety of regulatory messenger compounds secreted by the myeloid cells and the lymphocyte cells. Through the secretion of these regulatory messenger compounds, the T-cells can regulate the proliferation and activation of other immune cells such as B-cells, macrophages, PMN and other T-cells. For example, upon binding a foreign antigen, a macrophage or other antigen presenting cell can secrete interleukin-1 (IL-1) which activates the Helper T-cells. T-cells in turn secrete certain lymphokines, including interleukin-2 (IL-2) and xcex3-interferon, each of which have a variety of regulatory effects in the cell-mediated immune response. Lymphokines are a large family of molecules produced by T-cells (and sometimes B-cells) including
IL-2, which promotes the clonal proliferation of T-cells;
MAF or macrophage activation factor, which increases many macrophage functions including phagocytosis, intracellular killing and secretion of various cytotoxic factors;
NAF or neutrophil activation factor, which increases many functions of the PMN including phagocytosis, oxygen radical production, bacterial killing, enhanced chemotaxis and enhanced cytokine production;
MIF or macrophage migration factor, which by restricting the movement of macrophages, concentrates them in the vicinity of the T-cell;
xcex3-interferon, which is produced by the activated T-cell and is capable of producing a wide range of effects on many cells including inhibition of virus replication, induction of expression of class II histocompatibility molecules allowing these cells to become active in antigen binding and presentation, activation of macrophages, inhibition of cell growth, induction of differentiation of a number of myeloid cell lines.
Activated macrophages and PMNs, which provide an enhanced immune response as part of the cell-mediated adaptive immunity, are characterized as having increased production of reactive oxygen intermediates. This increased production of reactive oxygen intermediates, or respiratory burst, is known as xe2x80x9cprimingxe2x80x9d. Certain lymphokines, such as xcex3-interferon, trigger this respiratory burst of reactive oxygen intermediates in macrophages and PMNs. Thus, lymphokines, such as xcex3-interferon, which are secreted by the T-cells provide an activation of these macrophages and PMNs which results in an enhanced cell-mediated immune response.
The immune response can provide an immediate or a delayed type of response. Delayed-type hypersensitivity is an inflammatory reaction which occurs in immune reactive patients within 24-48 hours after challenge with antigen and is the result primarily of a cell-mediated immune response. In contrast, immediate-type hypersensitivity, such as that seen in anaphylactic or Arthus reactions, is an inflammatory reaction which occurs in immune reactive patients within minutes to a few hours after challenge with antigen and is the result primarily of humoral or antibody-mediated immune response.
The ability of the immune system, and in particular the cell-mediated immune system, to discriminate between xe2x80x9cselfxe2x80x9d and xe2x80x9cnon-selfxe2x80x9d antigens is vital to the functioning of the immune system as a specific defense against invading microorganisms. xe2x80x9cNon-selfxe2x80x9d antigens are those antigens or substances in the body which are detectably different or foreign from the animals own constituents. xe2x80x9cSelfxe2x80x9d antigens are those antigens which are not detectably different or foreign from the animals own constituents. Although the immune response is a major defense against foreign substances which can cause disease, it cannot distinguish between helpful and harmful foreign substances and destroys both.
There are certain situations, such as with an allogeneic transplant or in xe2x80x9cgraft versus hostxe2x80x9d disease, where it would be extremely useful to suppress the immune response in order to prevent the rejection of helpful foreign tissue or organs. Allogeneic tissues and organs are tissues and organs from a genetically different member of the same species. xe2x80x9cGraft versus hostxe2x80x9d disease occurs where the transplanted tissue, for example in a bone marrow transplant, contains allogeneic T-cells of the donor which cause an immune response against the recipient""s own tissues. Although both humoral and cell-mediated immune responses play a role in the rejection of allogeneic tissues and organs, the primary mechanism involved is the cell-mediated immune response. Suppression of the immune response, and in particular, suppression of cell-mediated immune response, would thus be useful in preventing such rejection of allograft tissues and organs. For example, cyclosporin A is currently used as an immunosuppressive agent in the treatment of patients receiving allogeneic transplants and in xe2x80x9cgraft versus hostxe2x80x9d disease.
There are times when the individual""s immunological response causes more damage or discomfort than the invading microbes or foreign material, as in the case of allergic reactions. Suppression of the immune response in these cases would be desirable.
Occasionally, the immunological mechanisms become sensitized to some part of the individual""s own body causing interference with or even destruction of that part. The ability to distinguish between xe2x80x9cselfxe2x80x9d and xe2x80x9cnot selfxe2x80x9d is impaired and the body begins to destroy itself. This can result in an autoimmune diseases such as rheumatoid arthritis, insulin-dependent diabetes mellitus (which involves the autoimmune destruction of the xcex2-cells of the islets of Langerhans which are responsible for the secretion of insulin), certain hemolytic anemias, rheumatic fever, thyroiditis, ulceractive colitis, myestheniagravis, glomerulonephritis, allergic encephalo-myelitis, continuing nerve and liver destruction which sometimes follows viral hepatitis, multiple sclerosis and systemic lupus erythematosus. Some forms of autoimmunity come about as the result of trauma to an area usually not exposed to lymphocytes such as neural tissue or the lens of the eye. When the tissues in these areas become exposed to lymphocytes, their surface proteins can act as antigens and trigger the production of antibodies and cellular immune responses which then begin to destroy those tissues. Other autoimmune diseases develop after exposure of the individual to antigens which are antigenically similar to, that is cross-react with, the individual""s own tissue. Rheumatic fever is an example of this type of disease in which the antigen of the streptococcal bacterium which causes rheumatic fever is cross-reactive with parts of the human heart. The antibodies cannot differentiate between the bacterial antigens and the heart muscle antigens and cells with either of those antigens can be destroyed. Suppression of the immune system in these autoimmune diseases would be useful in minimizing or eliminating the effects of the disease. Certain of these autoimmune diseases, for example, insulin-dependent diabetes mellitus, multiple sclerosis and rheumatoid arthritis, are characterized as being the result of a cell-mediated autoimmune response and appear to be due to the action of T-cells [See Sinha et al. Science 248, 1380 (1990)]. Others, such as myestheniagravis and systemic lupus erythematosus, are characterized as being the result of a humoral autoimmune response [Id.].
Suppression of the immune response would thus be useful in the treatment of patients suffering from autoimmune diseases. More particularly, suppression of cell-mediated immune response would thus be useful in the treatment of patients suffering from autoimmune diseases due to the action of T-cells such as insulin-dependent diabetes mellitus, multiple sclerosis and rheumatoid arthritis. Suppression of humoral immune response would be useful in the treatment of patients suffering from T-cell independent autoimmune diseases such as myestheniagravis and systemic lupus erythematosus.
The present invention provides novel compounds of the formula (1) 
wherein
the substituent in the three position on the cyclopentanyl ring is in the TRANS configuration relative to the bicyclic substituent,
Y3, Y5, Y7, Y8 and Y9 are each independently nitrogen or a CH group,
R is hydrogen, C1-C7 alky acyl or aryl acyl,
Q is NH2, halogen or hydrogen, and
Z is hydrogen, halogen, or NH2;
or a pharmaceutically-acceptable salt thereof.
The present invention also provides a method of effecting immunosuppression, and more specifically, a method of suppressing adaptive immunity, in a patient in need thereof comprising administering to said patient an effective immunosuppressive amount of a compound of formula (1).
In addition, the present invention provides a pharmaceutical composition comprising an effective immunosuppressive amount of a compound of formula (1) in admixture or otherwise in association with one or more pharmaceutically acceptable carriers or excipients.
As used herein the term xe2x80x9chalogenxe2x80x9d refers to monovalent iodine, bromine, chlorine or fluorine radicals, the term xe2x80x9cnitrogenxe2x80x9d refers to a trivalent nitrogen radical and the term xe2x80x9cCH groupxe2x80x9d refers to a methylidyne radical.
As used herein, the term C1-C7 alkyl acyl is composed of an acyl substituent combined with a C1-C7 alkyl substituent. The term acyl refers to a radical of a carboxylic acid created by the removal of the hydroxide from the carboxy group [xe2x80x94C(O)xe2x80x94]. The term C1-C7 alkyl refers to the hydrocarbon radical which may be derived from an alkane having from 1 to 7 carbon atoms in a straight chain or branched chain configuration. The combination of a C1-C7 alkyl radical with the acyl radical results in the C1-C7 alkyl acyl term. Included within the scope of the term C1-C7 alkyl acyl are the methyl acyl CH3xe2x80x94C(O)xe2x80x94, ethyl acyl CH3CH2xe2x80x94C(O)xe2x80x94, n-propyl acyl CH3CH2CH2xe2x80x94C(O)xe2x80x94, isopropyl acyl (CH3xe2x80x94)2CHxe2x80x94C(O)xe2x80x94, n-butyl, acyl CH3(CH2)3xe2x80x94C(O)xe2x80x94, sec. butyl acyl CH3CH2CH(CH3)xe2x80x94C(O)xe2x80x94, and the like.
The aryl acyl term refers to the radical composed of an acyl substituent and an aryl substituent. The term acyl refers to a radical of a carboxylic acid created by the removal of a hydroxide ion from the carboxyl group [C(O)xe2x80x94]. The term aryl refers to the group that remains after the conceptual removal of a hydrogen from a ring position of a benzene or a substituted benzene nucleus or a nicotinoyl. The benzene nucleus may be optionally substituted with up to three substituents selected from the groups consisting of Cl, Br, F, I, C1-C4 alkyl, NH2, or OH. Included within the scope of this term are benzoyl C6H5xe2x80x94C(O)xe2x80x94, p-chlorobenzoyl C6H4Clxe2x80x94C(O)xe2x80x94, 4-fluorobenzoyl C6H4Fxe2x80x94C(O)xe2x80x94, o-toluyl CH3C6H4xe2x80x94C(O)xe2x80x94, nicotinoyl C5H4Nxe2x80x94C(O)xe2x80x94, and the like.
As used herein, the term xe2x80x9cC1-C4 alkylxe2x80x9d refers to a saturated straight or branched chain hydrocarbyl radical of one to four carbon atoms and includes methyl, ethyl, propyl, isopropyl, tertiary butyl, and the like.
As used herein, the term xe2x80x9cpharmaceutically-acceptable saltsxe2x80x9d refers to acid addition salts of the compounds of formula (1) wherein the toxicity of the compound is not increased compared to the non-salt. Representative examples of pharmaceutically-acceptable salts, which are made by treating the compounds of formula (1) with the corresponding acids, are: hydrobromide, hydrochloride, sulfuric, phosphoric, nitric, formic acetic propionic, succinic, glycolic, lactic, malic, tartaric, citric ascorbic, xcex1-ketoglutaric, glutamic, aspartic, maleic, hydroxymaleic, pyruvic, phenylacetic, benzoic, para-aminobenzoic, anthranilic, para-hydroxybenzoic, salicylic, para-aminosalicylic, methanesulfonic, ethanesulfonic, hydroxyethanesulfonic, ethylenesulfonic, halobenzenesulfonic, toluenesulfonic, naphthalenesulfonic and sulfanilic acids. The hydrochloride is preferred as the pharmaceutically-acceptable salt of compounds of formula (1).
It is understood that the substituents on the cyclopentanyl ring of the compounds of formula (1) have a TRANS configuration relative to the bicyclic substituent. It is further understood that the compounds of formula (1) may exist in stereoisomeric configurations. The compounds of formula (1) encompass and include both the individual stereoisomers and racemic mixtures.
A general synthetic procedure for preparing compounds of formula (1) wherein Y9 is nitrogen is set forth in Scheme A. 
The 1-hydroxy of cis-3-acetoxycyclopentan-1-ol is derivatized with a suitable leaving group (L) in step a of Scheme A. The particular leaving group can be one of many which are well known and appreciated in the art. Representative examples of suitable leaving groups are brosyl, tosy, mesylate. The preferred leaving group for step a is the mesylate.
In step b the leaving group of the cyclopentane derivative formed in step a is displaced with the desired nucleoside base, forming the trans-carbocyclic nucleoside analog. The preferred base for step b is adenine. When the 3-acetoxy analog is desired, the product of step b may be isolated or converted to the appropriate salt using procedures well known and appreciated in the art.
In step c the acetoxy group may be hydrolyzed with a base such a potassium carbonate to an alcohol according to procedures which are well known and appreciated in the art. When the 3-hydroxy analog is preferred, the product of this reaction may be isolated or converted to the appropriate salt using procedures well known and appreciated in the art.
In step d the 3-hydroxyl group may be converted to other alkyl acyl or aryl acyl (Rxe2x80x2) analogs by techniques which are well known and appreciated in the art. For example if the benzoyl derivative is desired, the 3-hydroxy carbocyclic nucleoside can be reacted with benzoyl chloride in the presence of base to form the 3-benzoyl analogue.